1. Hungry: If your cat does not eat enough food at night, it may feel hungry in the early hours of the morning and start to cry. To solve this problem, you can provide your cat with enough food at night and feed it small snacks before going to bed to avoid it feeling hungry in the early morning hours.

2. Biological clock: Cats’ biological clocks may affect their sleep and activity times. If your cat is used to being active and playing in the early hours of the morning, they may wake up at this time and start to cry. To solve this problem, you can try changing your cat's sleep schedule, such as playing with it in the evening to make it more tired at night so that it can sleep more deeply at night.

3. Lack of activity: If your cat doesn’t get enough activity during the day, it may become bored at night and start barking. To solve this problem, you can provide your cat with adequate activity and play time during the day, such as using cat toys or setting up a climbing frame in your home.

4. Illness or discomfort: If your cat behaves abnormally at night, such as barking frequently or running around the room, it may be because they are experiencing a health problem or discomfort. It is recommended that you take your cat to the veterinarian for a check-up.

5. Social needs: Cats are social animals, and if they feel lonely or need attention at night, they may bark in the early hours of the morning. You can spend some time with your cat before bed, or consider adopting a companion.

6. Not adapting to the environment: If cats have recently moved or their environment has changed, they may feel anxious or uncomfortable at night and start to cry. You can try to create a comfortable environment for your cat and relax it before bed, such as giving it a gentle massage or listening to soft music.

7. Estrus: Unneutered cats will show frequent shouting and activity during estrus. To avoid this, it is recommended that cats be neutered.